On Sat, Jun 12, 2021 at 11:18 PM Matthias Maennich <maennich@xxxxxxxxxx> wrote: > > To avoid unnecessary recompilations, mkcompile_h does not regenerate > compile.h if just the timestamp changed. > Though, if KBUILD_BUILD_TIMESTAMP is set, an explicit timestamp for the > build was requested, in which case we should not ignore it. > > If a user follows the documentation for reproducible builds [1] and > defines KBUILD_BUILD_TIMESTAMP as the git commit timestamp, a clean > build will have the correct timestamp. A subsequent cherry-pick (or > amend) changes the commit timestamp and if an incremental build is done > with a different KBUILD_BUILD_TIMESTAMP now, that new value is not taken > into consideration. But it should for reproducibility. > > Hence, whenever KBUILD_BUILD_TIMESTAMP is explicitly set, do not ignore > UTS_VERSION when making a decision about whether the regenerated version > of compile.h should be moved into place. > > [1] https://www.kernel.org/doc/html/latest/kbuild/reproducible-builds.html > > Cc: Masahiro Yamada <masahiroy@xxxxxxxxxx> > Cc: linux-kbuild@xxxxxxxxxxxxxxx > Signed-off-by: Matthias Maennich <maennich@xxxxxxxxxx> > --- Applied to linux-kbuild. Thanks. > scripts/mkcompile_h | 14 +++++++++++--- > 1 file changed, 11 insertions(+), 3 deletions(-) > > diff --git a/scripts/mkcompile_h b/scripts/mkcompile_h > index 4ae735039daf..a72b154de7b0 100755 > --- a/scripts/mkcompile_h > +++ b/scripts/mkcompile_h > @@ -70,15 +70,23 @@ UTS_VERSION="$(echo $UTS_VERSION $CONFIG_FLAGS $TIMESTAMP | cut -b -$UTS_LEN)" > # Only replace the real compile.h if the new one is different, > # in order to preserve the timestamp and avoid unnecessary > # recompilations. > -# We don't consider the file changed if only the date/time changed. > +# We don't consider the file changed if only the date/time changed, > +# unless KBUILD_BUILD_TIMESTAMP was explicitly set (e.g. for > +# reproducible builds with that value referring to a commit timestamp). > # A kernel config change will increase the generation number, thus > # causing compile.h to be updated (including date/time) due to the > # changed comment in the > # first line. > > +if [ -z "$KBUILD_BUILD_TIMESTAMP" ]; then > + IGNORE_PATTERN="UTS_VERSION" > +else > + IGNORE_PATTERN="NOT_A_PATTERN_TO_BE_MATCHED" > +fi > + > if [ -r $TARGET ] && \ > - grep -v 'UTS_VERSION' $TARGET > .tmpver.1 && \ > - grep -v 'UTS_VERSION' .tmpcompile > .tmpver.2 && \ > + grep -v $IGNORE_PATTERN $TARGET > .tmpver.1 && \ > + grep -v $IGNORE_PATTERN .tmpcompile > .tmpver.2 && \ > cmp -s .tmpver.1 .tmpver.2; then > rm -f .tmpcompile > else > -- > 2.32.0.272.g935e593368-goog > -- Best Regards Masahiro Yamada
